I do not recall the names of the various Winchester models. But there are a couple of notable differences.

In the 1980's, the Win. M70 in .458 had a bit of a monte carlo cheekpiece. Today they have a straight comb. The monte carlo generally makes the gun less valuable.

A bit earlier than that they were a push feed system, which also makes them less desirable.

Do you have any pics of the rifle?